In telecommunications, a diversity scheme improves quality and reliability of a signal by using two or more communication channels with different characteristics. Diversity plays an important role in combating fading and co-channel interference and avoiding error bursts. It is based on the fact that individual channels experience different levels of fading and interference. Multiple versions of the same signal may be transmitted and/or received and combined in the receiver.
Antenna diversity, also known as space diversity, is a wireless diversity scheme that uses two or more antennas to improve quality and reliability of a signal. In a receiver of a mobile station, receiving diversity by means of two or more antennas is used to offer a possibility of enhanced channel diversity and improve receiving quality of the mobile station.
However, there are at least two problems in using the receiving diversity. Firstly, the receiving diversity increases power consumption. Secondly, in some scenarios where attenuation of different antenna paths may be very high, the receiving diversity degrades performance.
One method to address the problem of power consumption increase is to include in a receiver of a mobile station a main antenna and a diversity antenna. The diversity antenna is turned on or off dynamically by using one or more receiving quality indicators, such as a Signal-to-Noise Ration (SNR), a Bit Error Ratio (BER), a Received Signal Strength Indicator (RSSI), in order to reduce power consumption while maintaining receiving quality at a certain level.
When the receiving quality is below a lower threshold, the diversity antenna is turned on to improve performance. When the receiving quality is above an upper threshold, the diversity antenna is turned off to save power.
However, this method fails to turn on or off the main antenna dynamically. This will become problematic in some situations. Furthermore, this method can not avoid performance degradation due to the receiving diversity.